Sometimes the term “tight integration” is used in the field of technology for the feature of different radio access technologies supporting each other or covering up for each other to provide an aggregated improved service. Tight integration aims to fulfil fifth generation (5G) wireless telecommunication user requirement (UE) such as very high data rates by user plane aggregation or ultra-reliability by user or control plane diversity. User plane aggregation is particularly efficient if New Radio (NR) and Long Term Evolution (LTE) offer similar throughput for a particular user so that the aggregation can roughly double the throughput. The occurrence of these cases will depend on the allocated spectrum, the coverage, and the load of the two accesses. Ultra reliability can be mandatory for some critical applications for which reliability and low latency are crucial to maintain.
In addition to these, it is worth to mention that the tight integration also provides enhancements to existing multi-radio access technology (RAT) features, such as load balancing and service continuity, thanks to a radio access network (RAN) level integration transparent to the core network (CN), e.g. by less signalling. In particular, service continuity will be desirable in early deployments since it can be expected that early NR deployments will provide islands of 5G coverage within a wider LTE coverage.
Multi-RAT aggregation and mobility between LTE and NR are features that are typically applied in radio resource control (RRC) “Connected” mode. However, tight integration and/or interworking, as currently called in 3GPP may also comprise interworking procedures when the UE is in a sleeping state (“Idle” mode in LTE) and/or some potentially new sleeping or low active state(s) in NR, as Third Generation Partnership Project (3GPP) is currently discussing the introduction of a state called Dormant or Connected Inactive where procedures would be similar to LTE Idle but with the UE and the network keeping some context information and re-establishing the connection via RRC Connection Resume procedure.
WO 2016/119423 A1 discloses a network connection method and device, where the method includes that a base station receives a request message, reported by a UE, for requesting a network connection, wherein the request message carries first indication information for indicating that the UE supports a multi-system tight-coupling capability, and the base station sends, based on the request message and to the UE, a configuration message for the UE to perform the network connection, wherein the configuration message carries second indication information for indicating that the UE adopts a multi-system tight-coupling manner to perform the network connection, wherein a network selection conflict may be avoided in the UE.
Thus, present solutions rely on solid knowledge at the access network node about UE capabilities, which implies requirements on corresponding signalling, e.g. as suggested by WO 2016/119423 A1. For cases where such knowledge and signalling is not feasible or desired, conflicts may still appear between network configurations and UE capabilities. It is therefore a desire to provide a solution to avoid or resolve such conflicts.